The present invention relates to a method and apparatus for packaging ultra fine powders into containers.
Ultra fine powders of less than 1 micron in unit dimension and particularly nanometric powders of less than 100 nanometres unit dimension have a high surface area to weight ratio. Due to the high surface energy the powders are easily contaminated and in some cases react vigorously with air. In order to keep the powders in an as-produced form it is necessary to store them in an unreactive medium such as inert gas and other fluid media. The present invention provides a way in which the powders can be cleared from the reaction production apparatus in a non-reactive environment and in a manner that is repeatable and suitable for mass production.
According to a first aspect of the present invention, there is provided a method for packaging ultra fine powders into containers in a controlled environment in a sealed apparatus in which the internal environment does not react with the powder and which comprises a powder delivery chamber to which a supply of the powder is supplied from the reaction production apparatus, the powder delivery chamber having a port for receiving a container, the port being selectively closable by a first valve which seals the port, wherein each container is closable by a second valve which seals the container; the method comprising the steps of closing the first valve to seal the port; attaching a container to the port; opening the first valve; with the second valve also open, introducing powder into the container; closing the first and second valves to seal the port and the container; and disconnecting the container from the port.
The use of the two valves one of which seals the port and the other of which seals the container allows the controlled environment within the apparatus to be preserved, and also provides a method which is suitable for mass production. The supply of the containers to the apparatus can readily be automated. Also, the method allows the powder to be supplied continuously to the powder delivery chamber, while the powder is removed as a batch process in the containers.
The first and second valves can be of any type which are capable of sealing the port or the container as the case may be. It is preferable for the valves to be operable independently of one another. Preferably, at least one of the first and second valves is a sliding gate type valve, in which a gate member is slidable between an open configuration in which it does not obstruct the port or the entrance to the container, and a closed configuration in which it seals against the port or the entrance to the container. Preferably, the plate is provided with at least one ramp surface which cooperates with a complementary ramp in a valve housing, whereby sliding of the plate with respect to the housing forces the ramp surface to ride up the ramp hence forcing the plate into sealing engagement with the port or container. Preferably, the port and/or container is/are surrounded by at least by one O-ring against which the plate is sealed.
It is possible that, as each container is processed, some reactive gas will leak into the powder delivery chamber of the apparatus. One way of reducing this problem is to house the lowermost part of the powder delivery chamber and the container being processed within a loading chamber filled with non-reactive gas. Preferably, the loading chamber is purged, hence purging the container.
However, even then, some reactive gas may come into contact with the powder. Therefore, preferably, a third valve is provided which is arranged to selectively isolate the part of the powder delivery chamber having the port from the remainder of the powder delivery chamber, thereby defining an intermediate chamber between the first and third valves, a supply of non-reactive gas is provided to the intermediate chamber, and a purge line leads from the intermediate chamber, the method further comprising purging the intermediate chamber with non-reactive gas with the first and third valves closed until the amount of reactive gas in the intermediate chamber reaches an acceptably low level.
According to a second aspect of the invention, there is provided a combination of an apparatus for packaging ultra fine powders into containers, and at least one container, the apparatus comprising a sealed unit arranged to contain a non-reactive environment, a powder delivery chamber arranged to receive a supply of powder, the powder delivery chamber having a port for receiving a container, the port being selectively closable by a first valve which seals the port; the container being closable by a second valve which seals the container, and the container having a surface which is arranged to sealably engage with the port.